# Stata: Correlation and Covariance

This post will illustrate how to:

1. Create a correlation matrix of variables using the `correlate` command.
2. Display a correlation matrix as a covariance matrix.
3. Obtain the statistical significance of a correlation using the `pwcorr` command.

## Correlation Matrix

We’ll use the auto dataset for this tutorial.

``````sysuse auto, clear
``````

We’ll create a correlation matrix of four variables — price, mpg, weight, and length.

``````correlation price mpg weight length
``````

Note: We can shorten the `correlation` command to `corr` for convenience.

## Covariance Matrix

If we want to create of covariance matrix, we simply add the `covariance` option to the `correlation` command.

``````correlation price mpg weigh length, covariance
``````

## Statistical Significance of a Correlation

The `correlation` command produces a clean correlation matrix (or covariance matrix with the `covariance` option). If we want to see the statistical significance of a correlation, we need to use the `pwcorr` command with the `sig` option.

``````pwcorr price mpg weight length, sig
``````